Preparation of cigarette filter tips



United States Patent Office Fatented July 24), 1965 This invention relates to filter tips and to their produc tion.

The use of cellulose acetate in cigarette filter tips is well known. Cellulose acetate is most frequently employed for this purpose in the form of non-porous continuous fi aments, since in this form it is more easily controlled in processing operations, and when arranged collectively in a filter wad, is known to act as filtration medium for tobacco smoke. The preparation of cellulose acetate by a spinning process is a long established art, and novel Ways of improving its effectiveness in filter wads, for example, by crimping, have hitherto been described. In all cases however the cellulose acetate has been prepar d by processes well known in the textile industry.

it has been proposed to use in cigarette filter tips flake cellulose acetate which has a porous micro-rugose or pitted surface termed active, Flake material possessing this broken or pitted surface is stated to be particularly efiicient in the filtration of tobacco smoke. This improvement is directly attributed to the nature of the surface. The active surface referred to above differs from cast film or spun fibre, or flake, which, by reasons of its method of production and/or processing, for example by contact with solvents or solvent vapours, or by layers of coating or adhesive, has a smooth and unbroken surface.

The active cellulose acetate may be impregnated into or coated on to one or both sides of a carrier matrix, such as, for example, paper tissue or natural or synthetic materials in the form of fabric, woven or non-Woven, or in the form of a loose fibre mat in which the fibres may be bonded or unbonded and parallel or criss-cross. This provides a substantially reinforced cellulose acetate sheet, possessing the micro-rugose active surface. Such a reinforced cellulose acetate sheet was produced as follows:

A matrix of cellulose fibres which had been previously sprayed with glacial acetic acid, was impregnated with a solution of 7.5 parts by Weight of cellulose acetate in 92.5

parts by weight of glacial acetic acid, to which 30 parts by weight of water has been added, the excess of the impregnating solution was squeezed out and the impregnated sheet was immersed in water between two perforated plates, so that the water was able to permeate the sheet while the sheet was maintained under slight pressure and held flat.

The formed sheet reinforced or otherwise may be cut up into shreds in the same way as tobacco, which can then be processed into filter wads, by the use of conventional cigarette manufacturing machines.

What we claim is:

1. A method for the manufacture of cigarette filters from cellulose acetate which has a pitted active surface comprising the steps of impregnating a fibrous sheet carrier with a solution of cellulose acetate which has added thereto a precipitant liquid in an amount adjusted to up preach the precipitation point, treating the so impregnated carrier with the precipitant to occasion in situ formation of the active cellulose acetate on the carrier the said impregnated carrier being adapted to be formed into a filter tip for association with a cigarette.

Z. A method for the manufacture of cigarette filters from cellulose acetate which has a pitted active surface comprising the steps of impregnating a fibrous matrix with a solution of cellulose acetate which has added thereto a precipitant liquid in an amount adjusted to approach the precipitation point, treating substantially all of the so impregnated matrix with the precipitant liquid to occasion in situ formation of the active cellulose acetate on the carrier the said impregnated carrier being adapted to be formed into a filter tip for association with a cigarette.

3. The process of claim 2 wherein the fibrous matrix is in the form of cut fibers selected from the group consisting of cellulose and cellulose acetate.

References Cited by the Examiner UNITED STATES PATENTS 1,640,596 8/27 Chatham 1l7-158 2,754,829 7/56 Hess 131208 2,759,853 8/56 Smith 1l7--166 2,780,228 2/57 Touey 131208 2,806,474 9/57 Yarsley 131-10 2,916,038 12/59 Wade 131-10 2,916,777 12/59 Crane et al 131-208 2,923,034 2/60 Dickie et al. 131-208 3,025,130 3/62 White 264168 3,060,501 10/62 Beal 264 FOREIGN PATENTS 838,419 5/52 Germany. 654,994 7/51 Great Britain.

SAMUEL KOREN, Primary Examiner.

MELVIN D. REIN, Examiner. 

1. A METHOD FOR THE MANUFACTURE OF CIGARETTE FILTERS FROM CELLULOSE ACETATE WHICH HAS A PITTED "ACTIVE" SURFACE COMPRISING THE STEPS OF IMPREGNATING A FIBROUS SHEET CARRIER WITH A SOLUTION OF CELLULOSE ACETATE WHICH HAS ADDED THERETO A PRECIPITANT LIQUID IN AN AMOUNT ADJUSTED TO APPROACH THE PRECIPITATION POINT, TREATING THE SO IMPREGNATED CARRIER WITH THE PRECIPITANT TO OCCASION "IN SITU" FORMATION OF THE "ACTIVE" CELLULOSE ACETATE ON THE CARRIER THE SAID IMPREGNATED CARRIER BEING ADAPTED TO BE FORMED INTO A FILTER TIP FOR ASSOCIATION WITH A CIGARETTE. 